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From "Jeff Eastman (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (MAHOUT-1045) Cluster evaluators returning bad results
Date Sun, 15 Jul 2012 14:58:34 GMT

    [ https://issues.apache.org/jira/browse/MAHOUT-1045?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13414652#comment-13414652
] 

Jeff Eastman commented on MAHOUT-1045:
--------------------------------------

Ok, I can duplicate your results, but (whew) the 500 clusters really takes a while to compute
CDbw inter-cluster density (it's n^2 on clusters) and it does it twice. First optimization
would be to cache it so the separation calculation can be done more quickly. I will dig into
the ClusterEvaluator NaN first. Stay tuned.
                
> Cluster evaluators returning bad results
> ----------------------------------------
>
>                 Key: MAHOUT-1045
>                 URL: https://issues.apache.org/jira/browse/MAHOUT-1045
>             Project: Mahout
>          Issue Type: Bug
>          Components: Clustering
>    Affects Versions: 0.6, 0.7, 0.8
>         Environment: Several environments and data sets
>            Reporter: Pat Ferrel
>             Fix For: 0.8
>
>
> With real world crawl data the Intra-cluster density from ClusterEvaluator is almost
always NaN. The CDbw inter-cluster density is almost always 0. I have also seen several cases
where CDbw fails to return any results but have not tracked down why yet.
> I have sent a link to an 8G data set that reproduces these errors to Jeff Eastman.

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